Field of the Invention
The invention relates to a transmission system, and more particularly, to an image transmission system and method with a finite re-transmission function.
Description of the Related Art
A real-time image transmission system is well adopted in many applications. For example, U.S. Pat. No. 8,265,171 discloses an error resilient video transmission system. An exemplary video transmission system is illustrated in FIG. 1. The video camera 102 captures video frames at a certain frame rate (e.g., 30 frames/second) and the captured video frames are then encoded by the video encoder 104. The video encoder 104 preferably may be a block-based hybrid video coding structure (e.g., MPEG-X, H.264) using motion compensated prediction (MCP) and transform coding (e.g., discrete cosine transform, DCT). Encoded (and compressed) video is then sent over a wire/wireless channel 108 using a transmitter 106. At the receiver side, once the receiver 110 receives a video packet, it produces an acknowledgement (instantaneous feedback) and sends it immediately over a wired/wireless feedback channel 120 to the transmitter 106, informing the transmitter 106/encoder 104 if the transmitted video packet was successfully received or damaged in the wired/wireless channel 108. In the meantime, the video packet is decoded by a decoder 112 and its reconstructed video is presented on display 114. Although shown separately, the encoder 104 and the transmitter 106 may be integrally formed and functioned as a single component. Likewise, the receiver 110 and the decoder 112 may also be integrally formed and functioned as a single component.
U.S. Pat. No. 8,265,171 is based on this instantaneous feedback information from the receiver 110. Specifically, its transmitter 106/encoder 104 determines how best to handle any lost packet(s) and how to encode the next captured video frame. As noted, the error-resilient real-time digital video transmission system is based on feedback from the receiver 110 regarding successfully transmitted or lost packets, along with synchronized error concealment that is performed at both the encoder 104 and the decoder 112.
Many network transmission systems use TCP/IP protocol, which re-transmit packets if a transmitter gets packet lost information by checking acknowledged packets from a receiver. The transmitter will keep re-transmitting if not receiving an acknowledgment from receiver. The property will guarantee the transmission correction, but it may not be suitable for real-time transmission. Besides, many real-time image transmission systems expect a DRAM-less solution to reduce cost. Accordingly, there is a need for a real-time image transmission system operating without using a DRAM buffer and with a finite re-transmission function.